Electroadhesive Clutches with Enhanced Force Capacity Using Soft Dielectric Interfaces

Abstract

Electroadhesive clutches with stiff dielectric films provide unique potential for programming stiffness and adhesion, but their low force capacities per unit area limit their applications. Reversible adhesives based on van der Waals forces leverage soft contact surfaces to achieve conformal contact and high adhesion, but such soft surfaces are challenging to use in electroadhesives as they add latent adhesion that reduces switchability. Herein, soft, elastomeric dielectrics that combine electrostatics and surface force-mediated adhesion are used to build electroadhesive clutches with high force capacity per unit contact area and voltage. Analytical models from fracture mechanics explain how clutch compliance, shape, and surface roughness affect force capacity and switchability. These models are used to design electroadhesives with soft dielectric films that achieve force capacities similar to those of state-of-the-art clutches with stiff dielectrics in terms of force capacity per unit area (22 N cm−2), but with simple dielectric materials with one-fifteenth of the relative permittivity. In addition, controlled surface roughness is used to increase the switchability of any given electroadhesive clutch design. Finally, the ability of soft dielectric clutches is demonstrated to enable programmable stiffness in reconfigurable robotic fabrics, structural elements, and robotic fingers.